The present invention relates to a camera, more particularly to a camera constructed to be sealed against water.
Cameras having movable lens barrels such as zoom lens barrels, for example, multifocus cameras and the like are arranged in such a manner that the total internal volume thereof varies as the lens barrel reciprocates. When the outside and inside of the camera are completely sealed, the air pressure within the camera sharply decreases as the lens is forwardly moved. Consequently, it becomes necessary to supply great force to the lens to move it forward. For this reason, it has been very hard to produce a completely water-proof camera.
In order to solve the aforementioned problem, the present assignee proposed a drip-proof camera having a breath hole (i.e., a venting hole) for making the inside and outside of the camera body communicable, i.e., permeable, with each other, in Japanese Utility Model Provisional Publication SHO 63-113137. In this case, the breath hole is covered with an air breathing but water-impermeable filter. The lens mounted on this camera therefore moves smoothly, whereas water is prevented from penetrating in an ordinary state of use, other than when immersed in water. The camera thus constructed is usable in any ordinary state as a drip-proof camera.
However, the breathing and water-impermeable filter used in such a drip-proof camera is limited in the amount of pressure it can withstand while preventing water penetration. As a result, the filter may break, thus allowing water penetration into the camera if the lens is forwardly moved while immersed in water by mistake. Particularly, in the case of a power-driven zoom lens camera, the switch for zooming operation may be operated by mistake (e.g., if it is touched by mistake) to cause the lens barrel to move back and forth when the camera is washed with running water or with water held in a basin after the camera has been used on the beach, for instance.
Further, in the case of a manual non-drip-proof camera such as a camera having a widely movable lens barrel, water may also penetrate into the lens through the sliding portion of the lens barrel when the lens barrel is backwardly or forwardly moved in the presence of water.